Process for treatment of lumber and other forest products



Patented June 24, 1947 PROCESS FOR TREATMENT OF LUER AND OTHER FOREST PRODUCTS .ioye C. Harm, San Francisco, Calif., assignor to Electric Steel Foundry, Portland, reg., a corporation of Oregon No Drawing. Application April 7, 194 i, Serial No. 530,062

13 Olaims. i

The present invention relates to processes for treatment of lumber and other forest products, and is particularly concerned with the solvent treatment of wood for the purpose of obtaining uniform moisture content in the wood and in order to remove the pitches and resins, and other soluble constituents from the wood.

In the sulphite pulp process it is important that the moisture content of the wood to be cooked be uniform. It is also important that the pitch and resin content of the wood be as low as possible.

Wood which is too dry is very difiicult to cook without charring and discoloration. Pitch causes foaming in the digester and consumes acid. The removal of the pitches and resins and the adjustment of the moisture content to a predetermined uniform percentage will give a superior cellulose pulp to that which can be obtained by the use of untreated wood. In addition to the improvement of the wood product for pulp, the resins and pitches, and other by-products removed from the wood may have a value which almost entirely offsets the cost of the treatment of the wood.

One of the objects of the invention is the provision of an improved method of treatment of wood by means of which the moisture content of the wood may be brought to a substantially uniform amount in order to render the wood in the best possible condition for use in the sulphite pulp process.

Another object of the invention is to render pitchy wood of variable moisture content suit able for cellulose fiber manufacture.

Another object of the invention is to render logging slash more suitable for sulphite treatment by adjusting the moisture content and distributing the moisture uniform y to each individual piece of wood so that the-moisture content will be uniform.

Another object of the invention is the provision of an improved process for adjusting the moisture content in chips of any sort of wood and for removing the pitches and resins so as to condition the chips to be more easily and completely digested by sulphite liquor.

Another object of the invention is the provision of an improved method of treatment of wood by means of a three-component solvent which is adapted to dissolve the pitch and resin in the wood more quickly and more readily and in greater amounts than the processes of the prior art and which permits the quick and easy recovcry of the pitches and resins from the solution.

desired in the finished product.

Another object of the invention is the provision of an improved and simple, economical method of recovery of the soluble constituents of wood in'a relatively pure form and separated from each other.

Other objects and advantages of the invention will be apparent from the following description; but, as the present process may be carried out by the use of many different standard types of apparatus of the prior art, no drawing is required to illustrate the invention;

The solventremployed in my method of treating wood is preferably a solvent having three components, one of which is an organic,'aliphatic solvent that is miscible with water,'such as,-for example, acetone. Other solventsthat maybe used are alcohol, methanol, and the like; but acetone is preferred'and the invention will be described with respect to the use of acetone} The other two components of thesolvent are preferably carbon tetrachloride and water, and in general the carbon tetrachloride maybe replaced by any other solvent whichjwill'form' a solution with acetone and which solvent per: se is immiscible in the acetone-water solution, such as, for example, trichlorethylene, trichloreth'a'ne, or chloroform. 1

Considering cost and all other factors, the'carbon tetrachloride is the other constituent solvent which I prefer to use with acetone and water in carrying out my process. v v

The proportions of thevarious components in the solvent solution may be varied. For example, the solution may include fifty percent of acetone and fifty percent of water, andadded to this mixture there may be carbon tetrachloride in the amount of ten percent ofthe volume ofthe acetone. More than fifty percent of water content is preferably not employed, as the rapidity with which pitch goes into solution is somewhat retarded by increased water content, and also in order to avoid the necessity for later distillation of the water-acetone solution; and in general only sufiicientwater is preferably employed to form an acetone-carbon tetrachloride solution'and a water-acetone solution, the two being immiscible. As one of the functions of the present treatment is to adjust the moisture content 'of the product, the amount of water used in the soluticn depends upon the moisture' content which is desired in the finished product. In all cases the strength of the acetone-water solution, before its application to the wet lumber, should be predetermined from the moisture content which is The moisture 3 content of the finished product would be substantially the same as the moisture content of the solution as it emerges from final treatment with the lumber. This naturally may differ from the initial moisture content of the solution if a considerable: amount of water is given ofi by the lumher or a considerable amount of water is taken on by the lumber. Therefore, the wet or dry condition of the lumber to be treated should also be taken into consideration so. that when the treatment has been finished the moisture contentwill be that which is desired.

Naturally, if a twenty-five percent moisture content is desired in the finished wood. instead: of a forty-five percent moisture content, the initial amount of water in the original acetone-carbon tetrachloride water solution would beless than if a forty-five percent moisture content were desired in the finished wood. The actual water content in the solution may be slightly greater or less than the desired moisture content of the finish-ed wood,.-depending on the relative wetness or dryness of the lumber being treated.

As tothe range of percentages for the constituents of the solution, good results can be obtained'when a start is made on wet lumber by using a-solutioncarrying from ninety-five percent to" fifty percent acetone relative to the water byvolumewith from five percent to twenty percent of carbon tetrachloride or other similar chemical substance relative to the volume of the acetone. These results are due to the fact that the acetone immediately 'withdraws water from thewct-wood, which causes the carbon tetrachlo- A ride to separate out of the solution, and naturally the pitchis extracted out'of the solution with the carbon tetrachloride.

To obtain the most rapid results, a solution of approximately eighty percent acetone relative to =a-watertcontent by volume would be the most effective. However, the effectiveness of theace- .tone solution is retarded very slightly down to a fifty percent water content when in the presence of carbon tetrachloride.

The effectiveness of the removal of pitch by the solution increases as the amount of water in the solution is diminished, and decreases as the .amount of water in the solution is increased; but the'solution isstill very eifective when as much as-fifty percentwater byvolume relative to the acetone content exists in the solution. The water .-content, however, is preferably determined by the water content desired in the finished product;--but when the amount of water content in the finished product is-of no consideration, then .the rapidity of pitch removal may be increased by diminishing the-amount of water so that the proportion of acetone relative to water by volume may beas high as eighty percent acetone, or even higher.

vA composite solvent of this nature forms two separate solutions, water-acetone solution, and

acetone-carbon tetrachloride solution. These twosolutions-do not mix, and are easily separated, :althoughthere are very minor quantities of carbon tetrachloride. in the Water-acetone solution and very minor quantities of water content in the :a'cetone-carbon tetrachloride solution.

:The solubilityof pitch in acetone is a function :of the purity-of the'acetone; and when water is present, the limit of solubility of the pitch decreases with increasin water content. The solu'bility of pitch in acetone-carbon tetrachloride lisrgr'eater than in water-acetone solution, as the water -content of the acetone-carbon terachloacetone solution.

ride solution is very low under all conditions, and both acetone and. carbon tetrachloride are extremely good solvents for pitch.

Carbon tetrachloride alone is not a good sol vent for pitch from wet wood, as it will not penetrate into the wood, due to the relative insolubility of carbon tetrachloride in water and the low solubility of water in carbon tetrachloride. However, in a mixture consisting of acetone, carbon tetrachloride, and water, the water-acetone solution penetrates the chips and rapidly dissolves the pitch to its soluble limit. The dissolved pitch is then rapidly transferred from the water-acetone solution to the acetone-carbon tetrachloride solution.

This .continually reduces the amount of dissolved pitch in the water-acetone solution so that this solution may continue to penetrate the chips and to dissolve the pitch from the wood.

Under these conditions, therefore, the water- .acetone mixture can never become saturated as longas the acetone-carbon tetrachloride solution can continue to take up the pitch from the water- .acetone solution and the maximum dissolving efficiency of the water-acetone solution is maintained.

I have found that the pitch content of the acetone-carbon tetrachloride solution can be built up to a very hi h percentage without in any Way retarding the dissolving tendency of the wateracetone component of the. mixture. This would not be the case if water and acetonev were used alone without carbon tetrachloride.

In the practice of the method, pitchy stumps or butt cuts, or other forms of wood may first be prepared in aform suitable for washing with the solution.

This preparation consists of either chipping or hogging the wood. The ultimate fineness is dependent to a great extent on the nature of the wood-and theamount of pitch and/or resins the wood contains.

After reducing the wood to the required size .ofparticles, it is charged into an extractor and humidiiying chamber, which consists of a tank that can be sealed from the. atmosphere. The

tank is then preferably closed, and the tank preferablypurged of oxygen .by either an inert gas or steam,.the air being removedv in order to eliminatethe-idanger of forming an explosive mixture with acetone vapors in the tank.

The tank may then be filled with the preadjusted. solution of acetone-water and carbon tetrachloride. The relative proportions of acetone and water should be such that there will be no tendency for moisture .to be withdrawn from the wood at more than a given desired percentage.

Woodbelow this moisture content will withdraw water from the water-acetone solution, While wood having more than the desired content of waterwill give up water to the water- This transferoi water from one wood particle to another will be accelerated by the removal or pitchy and resinous material from the-Wood. The chips may be soaked for a predete- -nined time in the three-component solution, or the solution may be continuously passed ov comminuted wood or wood chips and withdrawn from the bottom of the chamber in which the chips are being treated.

This is continued, the liquid being withdrawn replaced by fresh liquid until the material issuing. from the bottom of the tank is substantially tire-e from dissolved pitches.

The specific gravity of acetone-tetrachloride solution is much greater than that of the Wateracetcne solution, so that the acetone-carbon tetrachloride solution readily separates from the water-acetone solution by gravity, and can be withdrawn from a separatory funnel with the pitch which it contains.

The water soluble constituents removed from the wood in the extraction chamber will remain with the water-acetone solution; and, if desired, these can be recovered in a residue by distillation of the water-acetone solution.

The pitches can be recovered from the acetonecarbon tetrachloride solution by distillation of this solution for the recovery of the pitch, and the distilled solvents may be returned to the chips. If it is not desired to recover the water soluble constituents of the water-acetone solution which passes out of the top of the separatory funnel, this solution may be returned directly to the chips.

Thus, the recovery of the dissolved pitch is greatly facilitated by the fact that the pitch is contained in the acetone-carbon tetrachloride solution having the greater specific gravity.

While I prefer to add the carbon tetrachloride component of the solution directly to the extraction chamber, in some modes of practice of the invention the wood may be treated first with 'the acetone-water solution. After this solution is withdrawn from the chamber for the removal of distilled pitch, sufficient carbon tetrachloride may be added to the withdrawn solution to separate the pitch from the solution by reason of the selective solvent action of this chlorinated solvent.

The continuous transfer of pitch from the waterncetone solution, to the acetone-carbon tetrachloride solution greatly increases the dissolving action of the acetone-water solution; and th refore it is preferred to apply the three-component solvent directly to the wood that is being treated.

In general, the water-acetone solution withdrawn from the chips would not need to be distilled, unless the water content exceeds fifty per cent. The solvent remaining in the chips may be driven ofi by the use of live steam with a simple reflux condenser in which only part of the water would be condensed, as I do not prefer a solution of more than eighty per cent acetone.

The acetone-carbon tetrachloride vapors would be condensed in the extraction chamber, and this would tend to heat the solutions in the chamber, making the pitches more soluble in the solvents.

The temperatures at which the processes may be carried out may be varied considerably, the application of extraneous heat increasing the tendency toward solubility of the pitches, but also increasing the tendency toward production of acetone vapors and carbon tetrachloride vapors. I prefer to carry out the process without the application of extraneous heat, except that it may be introduced by the use of live steam in driving the air out of the chamber or in removing the solvent from the treated chips.

The present process is thus adapted to provide a, simple economical method of recovery of the acetone-carbon tetrachloride soluble constituents of the wood, as well as the water-acetone-soluble constituents in a relatively pure form and separated from each other.

The three-component mixture will dissolve the pitch from wet wood much more readily than commercial acetone or a solution of acetone and water. The pitch can be concentrated in a relatively small volume by the use of the carbon tetrachloride in limited quantities, as substantially all the pitch is contained in the acetonecarbon tetrachloride solution.

The use of a non-inflammable solvent, such as carbon tetrachloride and chlorinated solvents, tends to reduce the fire hazard in the extraction apparatus, but my invention includes the use of other organic solvents mentioned above, which may be inflammable and which accomplish the same results.

The moisture content in the wood that has been treated is substantially uniform throughout the various particles of the wood; and the pitch having been removed, the treated wood is in the best condition to be used to produce a superior cellulose pulp.

As the constituents of the solvent mixture may be used over and over again, the present process is economical in the use of materials.

While I have illustrated a preferred embodiment of my invention, many modifications may be made without departing from the spirit of the invention, and I do not wish to be limited to the precise details of the process set forth, but desire to avail myself of all changes within the scope of the appended claims. 1

Having thus described my invention, what I claim as new and desire to secure by Letters Patent of the United States, is:

1. The method of treatment of wood for the removal of the pitch which comprises subjecting the wood to the dissolving action of water and acetone to dissolve the pitch, and segregating the pitch from the water-acetone solution by the action of carbon tetrachloride in an amount of 5% to 20% by volume of the acetone, which combines with part of the acetone to form an acetonecarbon tetrachloride solution to which the pitch is transferred from the water-acetone solution.

2. The method of treatment of wod for the removal of the pitch which comprises subjecting the wood to the dissolving action of water and acetone to dissolve the pitch, and segregating the pitch from the water-acetone solution by the action of carbon tetrachloride in an amount of 5% to 20% by volume of the acetone, which combines with part of the acetone to form an acetone-carbon tetrachloride solution to which the pitch is transferred from the water-acetone solution, and distilling the acetone-carbon tetrachloride solution to separate the pitch as a residue and to return the acetone-carbon tetrachloride liquid for further use.

3. The method of removing Water-soluble constituents and pitch from wood, which comprises subjecting the wood to the action of a threecomponent solution containing water, acetone, and carbon tetrachloride in such manner that a water-acetone solution is formed containing the water-soluble constituents and an acetonecarbon tetrachloride solution is formed containing the pitch constituents, the pitch being dissolved out of the wood by the water-acetone solution and transferred to the acetone-tetrachloride solution.

4. The method of removing Water-soluble constituents and pitch from wood, which comprises subjecting the wood to the action of a threecomponent solution containing water, acetone,

and carbon tetrachloride in such manner that a water-acetone solution is formed containing the 7 water-soluble constituents and an acetone-carbon 7 te'trachloridesolution is formed containing the "pitch" constituents, the pitch being dissolved out -of the-wood "by thewater-acetone solution and -trarisferred to the acetone-tetrachloride solution,

and separating the latter solution from the "'efiiuentsby 'vir'tue 'ofthe difference in specific agravity.

5. iThexmethod of removing-water-soluble constituents and pitch from wood, which comprises subjecting the wood to the action of a three-com ponentsolution containing water, acetone, and

carbon tetrachloride in such manner that a "water-'acetonesolution is formed containing the water-solubleconstituents 'and an acetone-car- -'b0n tetrachloride solution is formed containing -the-pitchfooristituents, the pitch being dissolved out of the wood by the water-acetone solution and transferred to the acetone-tetrachloride solution,- an'd'separating the latter solution from the "efliuentbyxvirtue of the difference in specific gravity, and distilling the water-acetone effluent -toiremove t-he'water-soluble constituents therefrom.

'6.'Themethod of removing water-soluble con- *-stit-uents and pitch from 'wood,.which comprises subjectingthe wood to the'action of a three-componentsolution containing water, acetone, and

carbon tetrachloride in such manner that a water-acetone 'solllti'onis formed containing the water-soluble constituents and an acetone-carbon tetrachloride solution is formed containing DhGEPitCh constituentsthe pitch being dissolved out of the wood by'the water-acetone solution "and transferred 'to the acetone-tetrachloride 'solution andseparating the latter solution from *thee'iilue'ntby virtue of the difi'erence in specific :gravity, and distillin'g the acetone-carbon tetrachloride efiiuent-toseparate the pitch from the distillate.

"YJThG method of extracting pitch from wood in which the wood istreated with a water solution of an aliphatic, water-soluble solvent 'for :pitch and simultaneously removing the pitch fremthefirst mentioned solvent by a second pitch solvent soluble in the organic aliphatic solvent -but insoluble in water, thereby constantly regenerating the'primary-pitch solvent and acceleratingthe removal of the pitch from the wood.

=8. The-method of treating wood, which comprises subjecting the wood'to a water solution containing a olvent for pitch-and other soluble constituents-of wood, and simultaneously segregating -the .pitch from the solvent solution by .means of a -chlori-nated organic aliphatic solvent 'for .pitch which'is immiscible with water and miscible with the firstmentioned solvent.

9.Theprocess of treating wood which com- ..prisesthe-steps of determining the'moisture content of the woodbefore treatment, subjecting the wood to a water solution containing a water 'soluble solvent forpitch and other soluble constituents of the wood and the water content of which solution is predetermined in relation to the; determined moisture content of the wood to produce a desired moisture content in the wood atter treatment and simultaneously separating said pitch and other soluble constituents from the solvent solution by the agitation therewith of a chlorinated organic aliphatic solvent for pitchwhich is immiscible with water and miscible inthe said water soluble solvent.

10. The process of treating wood which 'comprises the steps ofdetermining the moisture content of'the wood before treatment, subjecting the -wood to a water solution of acetone having a percentage of water determined in relation to that of the wood to provide the desired moisture content in the treated wood, and simultaneously admixing with the acetone solution a chlorinated organic aliphatic solvent for pitch which is miscible with the acetone and immiscible in water,

-the-admixed amount of said chlorinated organic carbon tetrachloride pitch solution to separate by gravity from the water-acetone-carbon tetrachloride mixture, draining ofi the separated carbon tetrachloride-pitch solution and distilling the carbon tetrachloride-pitch solution to separate'the pitchas a residue and reclaim the carbon tetrachloride.

12. The method of treating wood, which comprises'the steps ofsubjecti-ng the wood to a water solution containing a primary water soluble solvent for pitch and other soluble constituents of wood, and simultaneously segregating the pitch from the primarysolvent olution during its action upon the wood by means of the agitation therewith of a chlorinated organic aliphatic solvent for pitch which is immiscible with water and miscible with said primary solvent.

13. The method of treating a pitch extraction solution containing water, acetone and pitch while said solution is in direct contact with wood from which pitch has been extracted and which comprises subjecting the said solution to the action of a chlorinated aliphatic hydrocarbon solvent which ismiscible with said acetone and immiscible in water for removing the ,pitch from the pitch-extraction solution, thereby regenerating the said extracting solution forpitch extraction and'accelerating further pitch-removing action of'the extracting solution.

JOY-E C. HAUN.

REFERENGES fii'liED ihe following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,339,575 Brick Sept. 6, 1921 Be. 19,749 Bent Nov. 12, 1935 1,523,578 -Bredlik Jan. 20, 1925 OTHER REFERENCES International Critical Tables, 1st edition, volume HI, pages 418, 419 422 and 4.25, pub. 1928 by McGraw-Hill Book Co. of N. Y.

Fitzgerald, The Paper Mill, Nov. 7, 1936, pp.

The Merck Index, fifth edition, page 4. 

